This invention relates to an acoustic transducer. In more detail, the invention relates to an ultrasonic transducer which is useful for high-temperature applications. In still more detail, the invention relates to a coupling wedge for use in a high-temperature transducer.
Ultrasonic transducers contain a slab of piezoelectric material which is mechanically strained on application of an external electric field and which generates an electric charge upon application of a mechanical stress. Reflections of the ultrasonic waves within the transducer produce disturbances as some are reflected often enough to produce spurious signals in the transducer and yet not often enough to be internally absorbed. Accordingly, transducers built for room temperature operation normally contain some plastic or rubber-like material to damp out the natural vibrations of the transducer components. However, materials with high internal loss exhibit such losses only in a narrow temperature range. At high temperatures such materials cannot be employed. Accordingly, standard commercially available ultrasonic transducers cannot be employed in a high-temperature environment such as that of a liquid-metal-cooled nuclear reactor wherein temperatures of 1000.degree.F. or more are met. One important utility for such a transducer would be in a flow meter in a liquid-metal-cooled fast breeder nuclear reactor. The transducer could also be used in an under sodium scanning system, liquid level indicators or in standard nondestructive testing equipment.